Couplers, or hitches as they are sometimes called, are often used to connect implements to the arms of excavators, earth moving machines, diggers, back hoes, etc. The couplers are sometimes also referred to as “pin grabber” couplers as they grab the two connecting pins that are attached to many implements for the purpose of connecting the implement to an arm.
The couplers allow implements to be changed quickly and efficiently by being able to release the connecting pins of one implement, and to grab the connecting pins of another, using a remotely controlled hydraulic actuator on the coupler.
The ability to quickly change implements however, has lead to an increasing number of accidents involving implements coming loose, or falling from excavators etc. Most couplers today will have a safety locking feature that will hold one of the pins of an implement if the coupler fails, or if the other pin comes free for some reason.
However, it is apparent that a single safety lock feature is not sufficient. Accidents are still occurring as a result of the use of these quick change couplers. What is required is a secondary safety locking feature, and sometimes also a tertiary safety locking feature, to provide an improved level of safety, even if there is a failure of the first safety lock.
However, this requirement has proven to be difficult to achieve. Couplers will often have a fixed jaw, and a movable jaw. While it may be relatively straight forward to provide a locking system for a fixed jaw, the provision of a locking feature that is associated with the movable jaw is more challenging.
In addition, safety locks need to be relatively simple, to ensure high levels of reliability of the locks. Couplers are often used in harsh environments, and often become covered in dirt or grit, and must be robust to continue to function in such conditions. Safety locks must therefore be as simple as possible, and be robust in the operation, to ensure reliability and safe operation.
Size and weight are also a factor with couplers. Couplers that are excessively heavy, or which are bulky and have too great a distance between their connection to the arm, and their connection to the implement, can significantly limit the performance of a machine such as an excavator. The greater this distance is, the greater is the reduction in the maximum “break-out” force of the machine, caused by the coupler.